Seeking knowledgeable
advice re replacing the shaft log, and associated drive train installations and alignment.
The patient is a 1986 Jonmeri 40. Using a cute custom-made tool crafted by a local machine shop (photo 1) after 2 days of effort, finally got the cutless bearing out and removed the prop shaft. This revealed extensive
corrosion at the in-board end of the shaft log tube, especially on the underside and under the retaining strap for the
Volvo dripless
shaft seal (photos 2&3). There are 1/8" diameter holes right through the stainless at the edge where the
Volvo seats. Lucky we didn't sink the
boat.
The
boat is
on the hard in Johor,
Malaysia. Given the policies, realities and
work force at this yard, this is going to be a
DIY job. The yard will not allow us to bring in any outside (i.e., qualified) labour. Before I start blindly grinding away I need a lot of information, a plan, and confidence.
Here are the relevant (and perhaps irrelevant) details I can offer (attempts to get info from the manufacturer in
Finland are in process, but so far frustrating):
The existing tube appears to be 50mm ID and 54mm OD, length approx. 30cm on top and 14cm on the bottom (cut at angle flush with hull). All other original stainless on this Baltic-built boat has held up beautifully so I presume it was top-quality high alloy 316 or 317. I now realize there was no cathodic protection for this tube. This boat design is non-bonded.
The Volvo
shaft seal was last changed 4 years ago; the tube had some deterioration but looked serviceable. The seal had been previously changed in 2004. At that time there was
corrosion along the 10-12mm inboard end of the tube. The corroded area was cut off and the Volvo seal was installed a bit further down the shaft on the still-intact remnant of tube.
The
hull is solid
fiberglass, approximately 35-40mm thick in this area. If there is a flange on the exterior
hull (photo 4), it is under layers of vinyl ester and barrier coat applied after
osmosis strip and
repair in 2007 (New Zealand's
Osmosis Solutions).
In addition to getting the new shaft log aligned and glassed in properly, the sequence and methods for
installation and alignment (out of and in the water) of the following drive train elements need to be worked out:
- new
engine mounts for the
Yanmar 4JH2E, yet to be installed.
- there is a
classic AquaDrive -- the
seals on 2 prior AquaDrives blew out due to less-than-optimal
engine alignment, but no problems for the last 9 years on this unit. I imagine that, at a minimum, the rubber mounting bushings should be replaced.
- adjusting the shaft coupling on the AquaDrive to correct the slight pulling of the shaft downward/to starboard that caused some uneven wear of the old cutless bearing.
- install new Volvo shaft seal.
- find and install new cutless bearing (unfortunately, 1 7/8" strut ID despite the 35mm shaft)
- the
current prop shaft is 35mm diameter, 1.53M long. We are about to
purchase a new FlexOFold, and we are very marginal on clearance under the hull and between the hub and strut. A new, longer shaft may be in order.
- new zincs on the shaft (finally, something easy!)
Oh, wait, and at some point here the rig (currently pretty slack) will be removed to install new
electronics. Putting the
mast up and retuning will tweak the hull.
So where to start? If anyone is willing to chime in on any or all of my questions, here is how I have attempted to categorize them:
1 - Pre-surgery prep: What do I need to measure and analyze, and how, before I start anything else? If I was fitting a
new boat, the placement and alignment of the shaft log would be a given before getting to prop shafts, engine mounts, etc., so it seems my objective should be to make the replacement shaft log exactly as when this Jonmeri left the factory.
2 -
Removal of corroded pipe: Should the objective be to remove the absolute minimum of surrounding
fiberglass, or does that leave a tougher job for bedding the new tube?
3 - Sourcing new tube, fabricating flange (assuming I can't get one from the manufacturer). I don't think I have a good option other than again using a high alloy stainless with about 2mm wall thickness. I need the 54mm OD to fit the Volvo seal (of which I already have spares), and I don't have room for a larger seal (e.g., PSS style). Quality stainless should allow the largest ID for
water flow inside the seal and around the shaft.
4 - Sequence for aligning everything - does this seem right:
1 - Install new cutless bearing in strut
2 - Install new bushings and adjust AquaDrive coupling (is this possible? how?) to true up prop shaft angle (machine shop has already confirmed that shaft is straight)
3 - Install prop shaft with new shaft log tube and Volvo seal threaded over shaft
4 - Center shaft log tube around shaft using shims, wedges -- I assume I want the shaft perfectly centered in the tube? That 50mm tube ID gives adequate clearance for any settling of the boat once it's in the
water, or when the backstay is tightened, rig adjusted, etc.
5 - Does it matter at what point I install the engine mounts and do the on-land alignment to the AquaDrive?
5 - Glassing in/bedding new tube -- is this just a sideways thru-hull, or do I need to use other techniques and materials?
5 - How to provide cathodic protection to the new shaft log?
Thank you in advance,
Alii (Laura, sv ZEN)